Composite materials and the mixtures thereof are very frequently used as packaging or as a structural element in construction and in mechanical engineering, for example. The physical properties of various materials are combined, in order to fulfill the desired mechanical functions. A further reason for the increasing use of composite materials is that they can be produced with lower material and energy outlay and therefore resources can be saved.
Various examples of such composite materials will now be described on the basis of following FIGS. 1 to 3.
FIG. 1 shows a composite material 1 made of a thin aluminum layer 2 of 20 to 40 μm in a sandwich with two layers 3 made of LDPE (low-density polyethylene) of 120 μm, which is used as a laminate for tubes. The aluminum is used as a barrier layer against light and prevents the diffusion of liquids and gases.
FIG. 2 shows the pattern of a printed circuit board 4 for electronic circuits, which consists of a composite of thin copper layers of 5 to 20 μm and glass-fiber-epoxy layers of 6 to 50 μm and more.
FIG. 3 shows a detail of an aluminum composite plate 7, which consists of two aluminum layers 8 of 200 to 500 μm and an interposed layer 9 made of HDPE (high-density polyethylene) of approximately 2 to 4 mm. Other plastics may also be used for this purpose. Such sandwich plates are used in facade construction or in vehicle construction.
Such composite materials cause great problems in the case of disposal, since precise separation of the individual materials is hardly possible. In rare cases, the composite materials are processed by means of thermal or wet-chemistry processes. These processes are typically not very efficient and substantially stress the environment. In addition, the recycled materials are frequently produced in inadequate quality. Another possibility is to crush the composite materials and mechanically separate the materials.
For example, a device for treating composite elements is known from WO-A-2006/117065, in which the composite material has been crushed to a grain size of 5 to 50 mm and the crushed particles are conducted in a feed channel to a breaking-up device. The device consists of a rotating rotor, having tools implemented as strips, which is arranged in a cylindrical stator. An air stream is conducted in the opposite direction in the ring space between rotor and stator from bottom to top, in order to discharge dust via a dust removal pipe attached on top. As the particles are broken up, they are crushed further when they impact on the strip-shaped tools, as described in greater detail in conjunction with FIG. 13. The air stream is necessary, on the one hand, to keep the particles for a sufficiently long time in the ring space and, on the other hand, to discharge the dust arising in this case upward.
Due to the air stream from bottom to top, the digested particles remain longer in the ring space than is necessary for the separation. Lighter and heavier particles thus also have a dwell time of approximately equal length in this ring space. Furthermore, the danger exists that the lighter particles will be drawn upward with the air stream, which results in further complications.